The method of delignification and bleaching of chemically welded lignocellulose pulp

 

(57) Abstract:

The inventive after processing lignocellulose pulp acid at pH 1 to 6 and flushing water to the slurry was added water-soluble compound containing magnesium in an amount of 0.01 10,00 kg/t of dry pulp, calculated on the magnesium, and pH is maintained within the range of 1 to 7, mostly 2 to 6. Then the pulp is bleached without chlorine reagent comprising hydrogen peroxide, at a pH of 8 to 12. As a water soluble compound containing magnesium, use of magnesium sulfate or magnesium chloride. Water-soluble compound containing magnesium, added at a temperature of 10 to 95°C for 1 to 180 min in the amount of 0.5 to 5.0 kg/t of dry pulp, calculated on the magnesium. 5 C. p. F.-ly, 8 PL.

The invention relates to the pulp and paper industry.

The known method of delignification and bleaching of chemically welded lignocellulose pulp, including the processing of pulp acid, such as sulfuric, nitric, at pH 1-6, washing with water and subsequent treatment with chlorine free bleaching reagent [1] However, the known method is not effective enough.

An object of the invention is to increase the whiteness of the pulp with reduced patrello add a water-soluble compound, containing magnesium in an amount of 0.01-10,00 kg/t of dry pulp, calculated on the magnesium, and pH is maintained within the range of 1-7, mostly 2-6.

The treatment with acid is an effective process for the removal of metal ions from the pulp containing lignocellulose. At the same time, it is known that ions of alkaline-earth metals, especially in its original position in the pulp, having a positive impact on the selective removal of lignin, as well as on the stability and the consumption of bleaching products that do not contain chlorine, such as peroxide, ozone and oxygen. This method represents an economical solution to the problem of creating a suitable profile with traces of metals for subsequent chlorine-free bleaching, in which undesirable metal ions are removed, while the added ions of alkaline-earth metals in General restore its position around the cellulose chains, and formerly occupied by ions of alkaline-earth metals. This is reached by adding compounds containing alkaline-earth metal, at this pH value and the temperature that the compound dissolves in water, thus providing the diffusion required to obtain the desired effect. The AOC is slotow and adding ions of alkaline-earth metals, in some cases you can do, which is an advantage for technology and economy of the process.

Bleach, chlorine-free, include inorganic peroxide compounds such as hydrogen peroxide and sodium peroxide, organic peroxide such as peracetic acid, and ozone, oxygen and dithionite sodium. Usually in random order or in a mixture, apply hydrogen peroxide (P), oxygen (O) and ozone. Preferably using hydrogen peroxide or a mixture of hydrogen peroxide and oxygen (RO). Particularly preferred sequence of R-3 or (RO)-3.

When processing bleaching agent without chlorine in alkaline pH value is usually adjusted by adding to the slurry of alkali or deletestream liquids such as sodium carbonate, sodium bicarbonate, caustic soda, oxidized sulfate mixture or slurry of magnesium hydroxide. Typically, the slurry of magnesium hydroxide is withdrawn from the system transport of chemicals in the production of sulphite pulp with magnesium as the basis.

Acid treatment is more convenient to acid. For this purpose apply nordwave chlorine, individually or in arbitrary mixtures. It is preferable to use sulfuric acid.

The preferred magnesium-containing compound is magnesium sulfate or magnesium chloride, or a mixture of magnesium-containing and calcium compounds such as calcium chloride or calcium oxide. It is preferable to use magnesium sulfate or magnesium chloride, and particularly preferred is magnesium sulfate. The combination of pH and temperature when adding compounds containing magnesium, is always selected so that the connection is in contact with the pulp would always be water solution.

During the process, which is the subject of the invention, the acid treatment is carried out at a pH value from about 1 to about 6, preferably in the range of from 1.5 to 5, and preferably in the range of from 2 to 4. It would be best to perform a treatment with an acid when the pH value from 2 to 3. If the use of magnesium sulfate or magnesium chloride, the addition is carried out at a pH value in the range from about 1 to about 7, preferably in the range from 2 to 6, preferably in the range of from 2 to 4. Especially preferably, this addition of magnesium osushestvleniya, the pulp is easier to handle at pH from about 8 to about 12, preferably at pH from 10 to 12. Processing other chlorine-free bleaching means, mentioned above, is in the normal range of pH for each of the whitening means, well known to any expert in this field of technology.

The treatment with an acid, a compound containing magnesium, and chlorine-free bleaching agent can be carried out at any stage of the sequence of operations of bleaching, for example, immediately after cooking, the pulp, or after the processing of oxygen. The method which is the subject of the present invention, it is better to apply to the pulp, from which the processing in the processing phase, the oxygen was removed lignin.

Within the scope of the present invention includes such an option in which the pulp during processing, the acid may be subjected to bleaching and/or processing in order to remove lignin. Means of whitening and/or removal of lignin, active in the pH range suitable for processing acid is, for example, chlorine dioxide, ozone, peracetic acid and/or peroxide compounds. Most conveniently be combined treatment with acid and acosada to chemical pulps from wood of deciduous and/or coniferous boiled according sulfite, sulfate, netronome or organorastvorimye the processes of pulping, or their modifications and combinations. More usable pulp, extracted from wood of deciduous and/or coniferous before according to the sulphate process, preferably sulphate pulp from hardwood.

The method of processing in accordance with the present invention can be applied to slurries containing lignocellulose with Kappa number in the range from about 5 to about 40, preferably 7 to 32, preferably from 10 to 20. In this case, the Kappa number is determined according to the standard method SCAN-C 1:77.

In the course of the method which is the subject of the present invention, the acid treatment is carried out at a temperature of from approximately 10 to approximately 95aboutC, preferably from 20 to 80aboutWith and preferably from 40 to 80aboutAnd during the period from 1 to about 120 minutes, preferably from 10 to 120 minutes and preferably from 20 to 40 minutes a Compound containing magnesium, added at a temperature of from approximately 10 to approximately 95aboutC, preferably from 40 to 80aboutAnd during the period from approximately 1 to priblizim is hydrogen peroxide, the pulp is treated at a temperature of from about 30 to about 100aboutC, preferably from 60 to 90aboutWith and within the period of time from about 30 to about 300 minutes, preferably from 60 to 240 minutes When handling acid and adding alkaline earth metal ions, the concentration of the pulp by weight may be from about 3 to about 35%, preferably from 3 to 15% by weight. When chlorine-free bleaching agent is hydrogen peroxide, the concentration of the slurry by weight may be from about 3 to about 50% by weight, preferably from 3 to 35% by weight and preferably from 10 to 25% by weight. Processing other chlorine-free bleaching means, mentioned above, is within the normal range of temperature, time and concentration of pulp for each bleaching tools, which are well known to specialists in this field of technology.

The number of compounds containing the magnesium is in the range from approximately 0.01 to approximately 10 kg/t of dry pulp, in terms of magnesium, preferably in the range from 0.5 to 5 kg/ton of dry pulp, calculated on the magnesium and preferably in the range of 2 to 4 kg/t of dry pulp, in lane is TBE chlorine-free bleaching means of hydrogen peroxide, the amount of hydrogen peroxide is in the range from about 2 to about 50 kg/t of dry pulp in the calculation of 100% hydrogen peroxide. The upper limit is not determinative, but is set to save. The amount of hydrogen peroxide should be in a desirable embodiment in the range from 3 to 30 kg/t of dry pulp, and preferably in the range from 4 to 20 kg/t of dry pulp, calculated on 100% hydrogen peroxide.

After treatment with acid, a compound containing magnesium, and chlorine-free bleaching agent slurry can be used directly for the production of paper with reduced requirements to white. On the other hand, the slurry can be increased to the desired degree of whiteness by processing in one or more stages. You can also conduct a final bleaching with chlorine-free bleaching products of the type specified above, optionally with intermediate operations alkaline extraction, which can be supplemented with peroxide and/or oxygen. This approach completely eliminates the formation and evolution of chlorine-containing organic substances (Oh). Comfortable is also performing a final bleaching with ozone in one or several stages. By processing in accordance with the invention can reduce the lignin content to a sufficiently low level even before will be applied HLT to be applied dioxide chlorine and/or hypochlorite without the formation of a large number of Oh.

Moreover, the application of the method which is the subject of the present invention, means that the brightness and Kappa number obtained pulp respectively higher and lower than those obtained with the ways in which compounds containing alkaline-earth metals are not added or added at higher pH value. In the method of bleaching chemical pulps objective is to achieve a high degree of whiteness and low Kappa number, the latter means a low content of dissolved lignin. At the same time, the consumption of chlorine-free bleaching remedies should be as low as possible, which means low processing costs. In the method, subject of the present invention, these objectives are achieved that can be seen from the examples. In addition, the concentration of the slurry, measured as viscosity, sufficient, which means that the pulp contains the cellulose chain, long enough to obtain a solid product.

P R I m e R 1. Sulphate pulp of softwood with Kappa number, 17, white 35% ISO and a viscosity of 970 DM3/kg is subjected to first-stage processing with sulfuric acid at pH of 2.0. The pulp is treated at a temperature of 60aboutWith over 30 mi is one solution, containing MgSO4that gives the concentration of magnesium in the pulp at the level of at least 500 million-1. During testing, the pH while adding ranges from 2.3 to 11.5 by adding sulfuric acid. Then the pulp is bleached with hydrogen peroxide at a temperature of 90aboutC. And the aging time and the concentration of the pulp is 180 min and 15% by weight, respectively. The final pH value is 11.5, and the addition of hydrogen peroxide is 15 kg/t of dry pulp at the rate of up to 100% hydrogen peroxide. For the purposes of comparison with the above conditions directly at the stage of application of hydrogen peroxide added magnesium, in accordance with accepted practice. For the purposes of comparison with the pulp when the above conditions treated only with sulfuric acid and hydrogen peroxide. The Kappa number, viscosity and white pulp are determined according to standard methods SCAN, and the consumption of hydrogen peroxide determined by iodometric titration.

The test results can be seen from the above table.1.

As you can see from the data table.1, the processing according to the present invention MgSO4at pH in the range from approximately 2 to approximately minimum to reduce viscosity and minimum consumption of hydrogen peroxide. In addition, from the comparison at pH of 2.3, one can see the importance of magnesium ions to improve whiteness, when in this case, the processing peroxide preceded only by the treatment with acid.

P R I m m e R 2. Delignifying oxygen sulphate pulp of softwood with Kappa number, 13,7, white 37,1% ISO viscosity 1057 DM3/kg is subjected to first-stage processing 15 kg of sulphuric acid per ton of dry pulp at a pH value of 1.9. The pulp is treated at a temperature of 50aboutC for 60 min, at a concentration of pulp 10% by weight. After washing the pulp with water at the second stage add from 0.1 to 1.5 kg of magnesium/t of dry pulp in the form of an aqueous solution containing MgSO4. Magnesium is added at pH of 4.1, at a temperature of 50aboutC for 60 min and at a concentration of pulp 3.5 by weight. Then the pulp is bleached with hydrogen peroxide at a temperature of 90aboutC, and the aging time and the concentration of the pulp are respectively 240 min and 10% by weight. The final pH value is 11.5, and the addition of hydrogen peroxide is 20 kg/t of dry pulp at a rate of 100% hydrogen peroxide. For comparison purposes the pulp is treated only with sulfuric acid and Perak the methods of the SCAN.

Results after bleaching with hydrogen peroxide can be seen from the data table.2.

As you can see from the data table.2, the implementation of the treatment with acid followed by the addition of dissolved magnesium and bleaching with hydrogen peroxide has a positive effect on the pulp in terms of Kappa number, viscosity and brightness.

P R I m e R 3. Delegirovano oxygen sulphate pulp of softwood, as in example 2 was processed in the sequence of operations D-AOR-3-R (experiment 1) and D-AOR-3-Mg-R (experiment 2), where the conditions at each stage is the same for both sequences. D and EOR belong to normal processing stage chlorine dioxide and normal phase alkaline extraction, supported respectively by hydrogen peroxide (P) and oxygen. C indicates the stage of processing with ozone at pH 2.3, Mg refers to the addition of 1 kg of magnesium /ton of dry pulp, in the form of an aqueous solution containing MgSO4. Magnesium was added when the pH value of 4.1, temperature 50aboutC for 30 min and the concentration of the slurry to about 3% by weight. R refers to the processing stage with hydrogen peroxide, where the pulp is treated at a temperature of 80aboutC for 120 minutes Final pH value of sostavit and whiteness are determined according to standard methods SCAN.

The results obtained after bleaching with hydrogen peroxide, can be seen from the above table.3.

As you can see from the data table.3, the addition of magnesium after initial treatment acid with ozone and bleaching with hydrogen peroxide has a positive effect on the viscosity and the white pulp.

P R I m e R 4. Delegirovano oxygen sulphate pulp of softwood, as in example 2 was processed in the sequence of operations stage I-R1-3-R2(experiment 1) and stage I-P1-3-Mg-P2(experiment 2), where the conditions at each stage is the same for both sequences. Stage I refers to the processing of ethylenediaminetetraacetic acid at pH 5. C indicates the stage of processing with ozone at pH equal to 2.3 and the concentration of the slurry of 10% by weight. Mg refers to the addition of 1 kg of magnesium/t of dry pulp in the form of an aqueous solution containing MgSO4. Magnesium was added when the pH is equal to 4.1, temperature 50aboutC for 30 min and the concentration of the slurry to about 3% by weight. P2relates to the processing stage with hydrogen peroxide, in which the pulp is treated at a temperature of 80aboutC for 120 minutes, the Final pH is about 11.5, and the addition of hydrogen peroxide reveals operations stage 1-R1-3-(PMg) (experiment 3). (PMg) refers to the addition of magnesium in the second stage treatment with hydrogen peroxide in alkaline medium under the conditions specified above, in accordance with established practice. Viscosity and whiteness are determined according to standard methods SCAN, and the consumption of hydrogen peroxide determined by iodometric titration.

The results obtained after the second stage of processing hydrogen peroxide shown in table.4.

As you can see from the table, the addition of magnesium in the range of pH values before bleaching by hydrogen peroxide has a positive effect on the viscosity and the whiteness of the pulp and reduces the consumption of hydrogen peroxide.

P R I m e R 5. This example illustrates the effect of pH values between 1 and 7 in stage 2, when you add a water-soluble compound containing magnesium. The treated pulp consisting of oxygen bleached sulphate pulp of softwood, which before treatment had a Kappa number, 18.1 and white 34,2%

The conditions:

Stage 1 (acid treatment): pH of 2.2, 50aboutC; 30 min; consistency pulp 10 wt.

Stage 2: 1 kg/t calculated by magnesium; 50aboutC, 60 min; the consistency of the pulp to 3.5 wt.

Stage 3:

The results are shown in table.5.

P R I m e R 6. This example illustrates the effect of the amount of magnesium added in stage 2. Pulp was the same as in example 5.

The conditions:

Stage 1 (acid treatment); pH 2.0; 50aboutC; 30 min; consistency pulp 10 wt.

Stage 2: pH 5; 50aboutC, 60 min; the consistency of the pulp to 3.5 wt.

Stage 3: 25 kg/t of hydrogen peroxide (H2ABOUT2); 90aboutWith; 240 min; final pH 11; consistency pulp 10 wt.

The results are shown in table.6.

P R I m e R 7. The example gives the experiments conducted with various water-soluble chemicals that contain magnesium. Thus, in the table.7 shows the effect of various water-soluble chemicals containing magnesium, on some intrinsic properties of the pulp after the acid treatment, adding a chemical containing magnesium, and subsequent bleaching with hydrogen peroxide according to the invention. The processed pulp is bleached with oxygen sulphate pulp of softwood tree, which before treatment has a Kappa number, 15,9, whiteness of 37.9% ISO viscosity 987 DM3/kg.

The conditions:

Stage 1 (acid treatment): pH 2,1; 50aboutC, 30 min; Sogni): 1 kg Mg/t of dry pulp; 50aboutC; 30 min; pH 4.5; the content of cellulose in the pulp of 3.5 wt.

Stage 3 (bleaching with hydrogen peroxide): 25 kg of hydrogen peroxide (H2ABOUT2)t of dry pulp; 90aboutWith; 240 min; final pH 11; the content of cellulose in the pulp 10 wt.

P R I m e R 8. This example gives the experiments conducted within a range of pH, including the boundary values at bleaching by hydrogen peroxide. Thus, in the data table.8 shows the effect of the final pH during bleaching with hydrogen peroxide on some intrinsic properties of the pulp after the acid treatment, adding a chemical containing magnesium, and subsequent bleaching with hydrogen peroxide. The processed pulp is bleached with oxygen sulphate pulp of softwood tree, which before treatment has a Kappa number 14, the degree of whiteness of 37.7% ISO and a viscosity of 950 DM3/kg.

The conditions:

Stage 1 (acid treatment): pH of 1.7; 50aboutC; 30 min; the content of cellulose in the pulp 10 wt.

Stage 3 (bleaching of hydrogen peroxide): 25 kg of hydrogen peroxide (H2ABOUT2) t of dry pulp; 90aboutWith; 240 min; the content of cellulose in the pulp 10 wt.

From the data table.7 and 8 shows that the selected chemicals and the interval for the MANUAL DELIGNIFICATION AND BLEACHING of CHEMICALLY WELDED LIGNOCELLULOSE PULP, includes treatment of the pulp with acid at pH 1 to 6, the washing water and the subsequent processing of chlorine-free bleaching reagent containing hydrogen peroxide at pH 8 to 12, characterized in that after the washing water to the slurry was added water-soluble compound containing magnesium in an amount of 0.01 to 10.0 kg/t of dry pulp, calculated on the magnesium, and pH is maintained within the range of 1 to 7, mainly 2 6.

2. The method according to p. 1, characterized in that the chlorine-free bleaching agent, a mixture of hydrogen peroxide and oxygen.

3. The method according to PP.1 and 2, characterized in that the pulp is treated with chlorine-free bleaching reagent containing hydrogen peroxide at pH 10 to 12.

4. The method according to p. 1, characterized in that as a water soluble compound containing magnesium, a mixture of magnesium and calcium compounds.

5. The method according to PP.1 and 4, characterized in that the water-soluble compound containing magnesium, consists of sulfate or magnesium chloride.

6. The method according to PP. 1 to 5, characterized in that the processing of pulp acid is carried out at 10 95oC for 1 to 120 min, and a water-soluble compound containing magnesium, add 10 95oWith over 1 180 mi wt. and the treatment of the pulp with hydrogen peroxide is carried out at pH 8 to 12.

 

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